The invention relates to a liquid crystal display device having a first liquid crystal cell between two polarizers and comprising a twisted nematic layer of liquid crystalline material having a twist angle .phi..sub.1 and a thickness d.sub.1, while the optical path length difference is d.sub.1..DELTA.n.sub.1 for incident light having a central wavelength .lambda..sub.0, said display device further comprising a compensating layer of optically anisotropic material having a twist angle .phi..sub.2 in the opposite direction.
Display devices of this type are used, for example in projection television. The difference .DELTA.n is the difference in refractive index for the ordinary and the extraordinary wave (anisotropy or birefringence).
A display device of the type described above is known from U.S. Pat. No. 4,443,065. With the aid of such a device, interference effect in a twisted nematic liquid crystal display device are eliminated as much as possible by means of a second twisted nematic liquid crystal cell which has preferably the same twist angle and the same optical path length difference. Notably the last-mentioned condition often imposes stringent requirements on the manufacturing process because a small tolerance in the thicknesses of the two composite cells is permitted when using one and the same liquid in the two cells (the same .DELTA.n).
The interference effects occur to an even stronger extent in liquid crystal display devices having a large twist angle .phi.. For these devices similar solutions have been given for double cells with .phi..sub.1 .noteq..phi..sub.2 in which an optimum relation is given between the twist angles and the associated values of d..DELTA.n. However, since these are passively driven display devices, this optimization focuses on drive properties (particularly a steep transmission/voltage characteristic curve) with which no high contrasts are achieved (they remain limited to about 10:1).